Set-screw.



-0. A. SMITH.

SET SCREW.-

APPLICATION FILED MAR. 25. 1-916.

Patented Jim 1 1918.

5 nvewtoz 050012 UNITED STATES PATENT onnion OSCAB A. SMITH, OF CLEVELAND, OHIO, ASSIGNOB, BY MESNE ASSIGNMENTS, TO THE NATIONAL-ACME COMPANY, OF CLEVELAND, OHIO, A CORPORATION DE -OHIO.

SET-SCREW.

Specification of Letters Patent. Patented June 18, 1918.

Application filed March-25, 1916. Serial No. 86,561.

To all whom it may concern:

Be it known that I, OSCAR A. SMITH, a citizen of the United States, residing at Cleveland, in the county State .of Ohio, have invented certaln new and useful Improvements in Set-Screws, of which the following is a specification.

This invention relates to improvements in Set Screws, the object of the invention be-' ing to provide a set 'scrcw having a; very strong tang or driving portion, for the reception of a suitable mating wrench therefor, and in which set screw there are no sharp corners to form a good starting point for breakage and which is extremely simple in construction and inexpensive to manufacture. v

In the drawings accompanying and forming part of this specification, Figure 1 is a.

side elevation of my nnproved set screw; Fig. 2 is also a side elevation thereof taken at right angles to Fig. 1; Fig. 3 is a top plan view showing the construction of the improved tang or driving portion of the screw; and Fig. 4: illustrates in perspective the improved set screw andthe mating end of its wrench.

Similar characters of reference indicate corresponding parts in the different figures of the drawings.

There are of course many forms of set screws in common use. For instance, the old headless or safety screw is made with a common screw driver slot, and of course could never be tightened .or set home strong enough with a screw driver, and for this reason many attempts have been made to produce a practical set screw that could be sufiiciently tightened, but all the forms with which I am familiar have proved very un-' satisfactory in use. instances of some of these attempts, there is a screw provided with a blind hexagon 'bore, and when tightening the same a hexagon shaped handle or" As stated,'however, all these forms of set screws have been Tound very unsatisfactory in use, slnce they cannot be made strong enough to withstand the tightening "strain of Cuyahoga' and 'mit thesame to of such tang.

of the wrench, the screws breaking rather than the wrench, and there is a tendency to open up the screw, in other words to crack it, and to avoid this it is impossible to tighten them up as they should be.

By means of the present improvement, however, the construction of the screw is such that an 'exceptionall strong tang or driving portion is provi ed, and while,the,

wrenclr or driving tool is sufliciently strong to properly set the screw .home for all practical requirements, the wrench is the weaker member, as it should be, or at least of substantially no greater strength than the driving portion of the screw, and there are no sharp corners either on the wrench or 'on the tang to afford opportunity for breakage.

The improved set screw shown in the drawings consists of the usual body 2 threaded throughout the major portion of its length, and provided at 1ts top or rear end with an im roved driving portion 3, which is formed y cuttingout on opposite sides of the screw an approximately semi.- circular or concave portion of suflicient depth to permit the wrench to properly grip such driving portion. This driving portion or tang 3 is formed with a'slight dish? or taper inwardly or toward the body of the screw, as shown in dotted lines in. Figs. 2 and 3, whereby the. wrench drives at the thickest portionof'the tang, since this por- 'tion of the tang. comes at thebottom of the with the tang or driving l'nember'of the screw, the sidewalls 6 of such groove being straight in the direction of the length of the wrench, instead of tapered, so as to perpass over the larger portion From the foregoing it will be observed portion of the screw and the convex formation of the wrench or driving tool provides off the driving portion'of the screw is elimi;

nated. Not only this, but the turning movevmentof the wrench or drivin tool, should there be any playbetween its driving porthat the concave formation of the driving tions and the tang of the set screw, will cause the interlocked portions to effectively engage each other to prevent slippage of one relatively to the other and thus avoid the twisting 0d of the tang or the eating ofi of the edges thereof.

The gist of the present improvement is the provision of a headless screw having a reinforced driving portion. In other words a driving portion that will be at least as strong as the driving member. State factory laws now compel manufacturers to use what is known as a headless or non-protruding screw on revolving parts of machines or shafts wherever there is a possible chance of workman coming in contact with the same. As hereinbefore stated there are several difi'erent types of headless screws on the market such as the Hollow Hex screw having a hexagon bore used with a mating hexagon bar or key; another type have a square bore; still another has a bore with dove tail grooves, but all these screws fail in one vital point, namely the means for tightening the screw is much stronger than the screw, therefore the screw breaks ofl before the driver. The common standard slot has the opposite fault, the driver is much too weak to stand the strain.

Before theState factory laws referred to, it was possible to use aset screw having a projecting square head whereon a' wrench could be used to bring it down tight, but these laws have made it impossible to continue the use of such a set screw and there: fore it is now compulsive to use a headless screw, yet they must be tightened down just as firm as the projecting square headed screw. The common slot set screw does not meet this test, the driver being too weak. If the slot is widened so that the driver is stronger than the screw then the latter is weakened and breaks. In thepresent invention the screw and driver by means of the construction herein shown and described has substantially equal strength, in other words, one is as strongas the other as can be readily seen by a careful inspection of Fig. 4 of the drawings in which the arrows indicate the points where the greatest strain of the driver upon the screw comes. At this point the driving tang or portion of the screw is the thickest.

I claim as my invention:

1. A headless machine set screw having .carrying portion of such tang.

a portion of its threads cut away to form a driving portion or tang gradually thickening outward from the axis of the screw to the threads thereof carried by such driving portion or tang whereby the driving portion or tang is of greater width at the threaded periphery of the screw than it is at the axis thereof, thereby to bring the strain of setting the screw on the thicker thereof, thereby to bringthe strain of setting the screw on the thicker portion of the tang, said driving portion also tapering slightly inwardly toward the body of the screw from the top of such driving portion whereby the driving portion at its top will be slightly thicker than at its bottom so that the strain on the driving tool constructed to conform to the driving portion or tang of the screw will come at the bottom of the groove thereof, and therefore at the strongest point of the driving portions of the driving tool.

3. The headless machine set screw of claim 1, in which the gradually thickening tang is of curved form at one or both sides,

thereof.

a. The headless machine set screw of claim 1, in which the tang thereof is of concaved form at both sides thereof the arc of each of which is longer than the con'vexedthread carrying portion of said tang.

5.The headless machine set screw of claim 2, in which the tang thereof is of curvedform at one or both sides thereof.

6. The headless machine set screwof claim 2, in which the tang thereof is of 'concaved form at both sides thereof the arc of each of which is longer than the convexed thread Si ed at Cleveland, in the county of Cuya oga and State of Ohio, this 21st day of March. 1916.

O SCAR A. SMITH. 

